In recent years, in mobile communication using radio waves, various information other than voice data such as image data and moving image data etc. has become the target of communication. In accordance with this, high-speed and large capacity radio data communication is also sought after. It is known that when high-speed transmission is performed in mobile communication, the influence of wave delays due to multipath cannot be ignored, and the reception performance deterioration may be caused due to frequency selective fading.
OFDM (Orthogonal Frequency Division Multiplexing) schemes have been a focus of attention as an example of a technological measure for frequency selective fading, and of these, various investigations have taken place into the MC (Multi Carrier)-CDMA schemes (also referred to as the OFCDM scheme) that is the combination with the CDMA (Code Division Multiple Access) scheme. MC-CDMA schemes are mainly classified into spreading in the time domain and spreading in the frequency domain (for example, refer to Non-Patent Document 1).
In a radio transmitting method using frequency domain spreading, a plurality of chips generated by spreading a modulated symbol are mapped onto different subcarriers at the same time. On the other hand, in a radio transmitting method using time domain spreading, a plurality of chips are mapped in a time sequence at the same frequency.
Also, in the MC-CDMA scheme, a plurality of channel coded data streams by modulation schemes or other transmission parameters etc. set individually can be code-multiplexed in the same frame. The reception performance of data streams vary depending on the settings of modulation schemes and parameters. For instance, there are cases where an excellent reception performance is obtained by using frequency domain spreading, and there are also cases where excellent reception performance is obtained by using time domain spreading (see Non-Patent Document 2, for instance).
Non-Patent Document 1: “A study on time domain spreading for OFCDM”, Technical Report of IEICE, RCS2001-179, 2001-11
Non-Patent Document 2: “VSF-OFCDM Using Two-Dimensional Spreading and Its Performance”, Technical Report of IEICE, RCS2002-61, 2002-05